JP5123161B2 - Harmful air pollutant collection method and apparatus - Google Patents

Description

  The present invention relates to a sample collection method and a collection device for measuring a trace amount of harmful air pollutants.

  Lower carbonyl compounds contained in trace amounts in automobile exhaust gas and ambient air are considered to be the main causative substances of health damage and are said to be one of harmful air pollutants. Among these, acrolein (acrylaldehyde) is positioned as the most important non-carcinogenic harmful substance in the US EPA (Environmental Protection Agency). However, since acrolein is very reactive and easy to change, it has been difficult to measure reliably without a good analytical method.

  The lower carbonyl compounds that are a kind of harmful air pollutants include formaldehyde, acetaldehyde, acetone, acrolein, metaacrolein, propionaldehyde, crotonaldehyde, benzaldehyde, butyraldehyde, valeraldehyde, tolualdehyde, hexaaldehyde, dimethylbenzaldehyde, glutaraldehyde Typical examples include methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetophenone, salicylaldehyde, nonanal, and the like.

On the other hand, among the lower carbonyl compounds, the analysis method for formaldehyde, which is a causative substance of allergy called sick house syndrome, is defined by JIS as follows.
(Non-Patent Document 1)
1) 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole spectrophotometry.
2) 2,4-Dinitrophenylhydrazine (hereinafter abbreviated as DNPH) Absorbing liquid collection-liquid chromatographic method or gas chromatographic method.
3) DNPH cartridge collection-liquid chromatography or gas chromatography.

In the method 1), formaldehyde in a sample gas is collected in a boric acid solution, then made basic, and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole is added to cause color development. Measure absorbance.
In the method 2), formaldehyde in the sample gas is collected in a DNPH absorption solution, extracted into chloroform, etc., and then re-dissolved in a solvent to suit the separation method as necessary. Or it introduce | transduces into a gas chromatograph and analyzes from the chromatogram.
The method 3) uses a cartridge obtained by impregnating and coating DNPH on an inorganic carrier such as silica gel (hereinafter referred to as a DNPH cartridge). Then, after the formaldehyde in the exhaust gas reacts with the DNPH in the DNPH cartridge to be derivatized into a hydrazone form and collected in the cartridge, the produced carbonyl compound derivative is eluted from the DNPH cartridge with a solvent, Analyze with liquid chromatograph or gas chromatograph and quantify from the chromatogram.

  In the methods 2) and 3), other carbonyl compounds of formaldehyde can be simultaneously collected, and therefore, they are used for simultaneous analysis. Among them, the liquid chromatographic method 3) is becoming a mainstream simultaneous analysis method because disposable cartridges are commercially available and the chromatographic operation is relatively simple.

FIG. 1 shows a schematic diagram of a conventional automobile exhaust gas collecting device.
Reference numeral 1 denotes an exhaust port of an automobile as an exhaust gas source, which can be connected to the sample conduit 11. The exhaust gas is sucked and sent to the sample conduit 11 and further to the DNPH cartridge 5 while the flow rate is controlled by the mass flow controller 6 by the pump 7. The tip portion of the sample conduit 11 is covered with a heat hose 2 that is heated and controlled by the temperature control device 10 so that moisture does not condense. The heating temperature is usually set to about 60 to 120 ° C. where moisture does not condense and DNPH does not decompose. A connector 3 connects the sample conduit 11 and the sample conduit 111 connected to the DNPH cartridge 5. The connector 3 can also have a filter function.

JIS K0303: 2004

Usually, a carbonyl compound collected by a DNPH cartridge becomes a DNPH-carbonyl compound, which is extracted with acetonitrile and then analyzed by HPLC.
However, acrolein, which is very reactive among carbonyl compounds, becomes DNPH-acrolein in the DNPH cartridge, and then reacts with DNPH quickly and continuously into DNPH dimers and trimers. There is a problem that the reaction proceeds and it cannot be detected as DNPH-acrolein, and accurate measurement has been impossible.

  Therefore, in the present invention, for the purpose of simply and accurately and accurately quantifying highly reactive acrolein and the like, it is one of harmful air pollutants, and it has been difficult to measure the collection of acrolein and the like. It is proposed to realize stable simultaneous analysis by suppressing the continuous reaction of DNPH and acrolein by sometimes cooling the collection cartridge.

  In particular, in the case of automobile exhaust gas, the gas is at a high temperature due to the engine operation, and it is necessary to be in a heated state so that moisture does not condense before being led to the collection device. Even with such a warm gas, sample collection is characterized by efficient cooling and accurate collection and analysis of acrolein and the like that are difficult to measure because the DNPH derivatization reaction proceeds continuously In the measurement of trace amounts of harmful air pollutants, the carrier impregnated with DNPH is cooled and the DNPH reacts with the lower carbonyl compound in the sample. A method for collecting a lower carbonyl compound.

  The method for collecting a lower carbonyl compound is characterized in that the cooling temperature is 10 ° C. or lower.

  The cooling is a method for collecting a lower carbonyl compound, wherein a collection cartridge provided with a carrier impregnated with DNPH is used.

  The collection is a method for collecting a lower carbonyl compound, wherein a collection cartridge filled with carrier particles impregnated with DNPH is used.

  Further, the collection is a method for collecting a lower carbonyl compound, wherein a collection cartridge provided with an integrated porous body impregnated with DNPH is used.

  Further, it is a method for collecting a lower carbonyl compound, wherein a buffering action for heat exchange of a sample is performed before the collection.

  The buffer action is a method for collecting a lower carbonyl compound, wherein a buffer cartridge provided with a carrier is used.

  The carrier for the buffer function is a method for collecting a lower carbonyl compound, wherein the carrier is silica gel.

  Further, in the collection of the sample, the sample is sent to the collection cartridge in which the carrier impregnated with DNPH is set next to the first stage and the buffer cartridge. It is.

  The lower carbonyl compound is acrolein, and is a method for collecting a lower carbonyl compound.

  In addition, the lower carbonyl compound is characterized in that a sample cartridge introduced into the low-temperature tank is detachably provided with a collection cartridge in which a carrier impregnated with DNPH is installed, and the temperature of the collection cartridge is freely controlled. It is a collection device.

  A lower carbonyl compound collecting device characterized in that a buffer cartridge is detachably provided upstream and upstream of a collecting cartridge of a sample conduit introduced into a low-temperature tank.

Details of the present invention will be described below.
FIG. 2 is a schematic view of a collection device according to the present invention. The same parts as those in FIG. 1 are given the same numbers. Reference numeral 3 denotes a connector which is connected to the sample conduit 11 connected to the sample conduit 11 and the buffer cartridge 4 in the cryostat 9.

  The connector 3 can also have a filter function. Reference numeral 6 denotes a mass flow controller that controls the collection flow rate, and is connected so that necessary components in the automobile exhaust gas as a sample can be collected by operating the collection pump 7.

  Reference numeral 10 denotes a temperature control device that can freely control the temperatures of the heat hose 2 and the low-temperature tank 9. The sample conduit 111 enters the cryostat 9 and is connected to discharge the sample out of the system through the mass flow controller 6 and the pump 7 through the buffer cartridge 4 and the collection cartridge 5 controlled by the aluminum block 8. ing.

  The pump 7 is operated and the mass flow controller 6 controls the flow rate to about 0.5 to 1 L / min, and the exhaust gas is drawn into the collection cartridge 5 for a certain period of time and is collected by reacting with DNPH as the collection material. . And the integrated flow rate (room temperature, dry gas conversion) at the time of collection is measured. After the collection, the collection cartridge 5 is plugged on both sides and proceeds to the extraction operation.

  Extraction is performed by adding a few mL (1 mL or more) of acetonitrile to the collection cartridge 5 after collection, transferring to a container, measuring up, and using as an analysis sample. An analytical sample is introduced into HPLC, and analytical measurement is performed based on detected peak information.

The collection cartridge 5 serving as a collection unit is installed in an aluminum block 8 in the low-temperature tank 9. At this time, the silica gel cartridge 4 as a buffer cartridge is connected to the upstream side of the collection cartridge 5. This is to perform a buffering action for sufficiently exchanging heat from the exhaust gas in a warm and humid state. The silica gel cartridge 4 is preferably the same size as the collection cartridge 5 and filled with silica gel not impregnated with DNPH.
A similar device is suitable for collecting ambient air, but if the temperature and humidity are not so high, the heat hose 2 and the silica gel cartridge 4 can be omitted.

  The collection cartridge 5 may be a luer chip type general-purpose cartridge in which an inorganic carrier gel impregnated with DNPH is filled in a polypropylene body and held by a frit. As the inorganic carrier, silica gel, titania gel, zirconia gel, or an organic substance and a hybrid thereof can be used. Can be used easily.

  Also, unlike the filling type, an integrated porous body having through-holes continuous in a three-dimensional network and pores formed on the inner walls of the through-holes is installed in the cartridge and used as a collecting material. The advantage is that the collected pressure can be kept low and there is no need for a frit to seal the particles. In the collecting method of the present invention, the inner diameter of the cartridge is preferably smaller than that of a general-purpose product so that cooling can be transmitted quickly and heat exchange can be performed, and the cartridge has a long shape to ensure the amount of collection. Is preferred. For example, an inner diameter of about 7 to 8 mm is used. In addition, if it is a luer chip type, the cartridges can be easily attached and detached.

The method of the low-temperature tank 9 is not limited as long as the collection cartridge 5 is sufficiently cooled. Various methods such as vapor compression type (compressor type), absorption type, electronic cooling type (cooling method using a Peltier type, semiconductor element called Peltier element), which are usually used for cooling, can be used. The free piston and styling cooler system, which has cooling efficiency several times that of the Peltier type, can be used at low temperature and energy saving.
Further, when the accuracy is not so required for the purpose of screening, the cartridges 4 and 5 can be simply used by covering them with a commercially available one-touch cooling pack.

  Hereinafter, the effects of the present invention will be clarified by examples.

FIG. 3 is a graph showing the recovery rate during extraction after a commercially available standard substance sample was diluted at room temperature, added to a DNPH cartridge, extracted with acetonitrile, as a preliminary experiment before collecting the sample.
<Experimental conditions> Addition:
Cartridge: inner diameter 12.7mm length 32mm
Collector: DNPH impregnated silica gel 120 μm 300 mg
Sample: (1) Acrolein low concentration (0.007 μg / mL)
(2) Acrolein high concentration (0.13 μg / mL)
(3) Formaldehyde low concentration (0.016μg / mL)
(4) Formaldehyde high concentration (0.25 μg / mL)
(Each is adjusted for high and low concentrations)
Addition amount: 30 μL

After extraction, HPLC:
Mobile phase: A: Water / acetonitrile = 50/50
B: Acetonitrile 100
Gradient: B: 0 to 60% (30 min) 60% (35 min)
Mobile phase flow rate: 1 mL / min
Column: Zorbax ODS 4.6 mmI. D. × (15 + 25cm)
Column temperature: 50 ° C
Detector: UV / VIS (wavelength 365 nm)
Injection volume: 10 μL
Analysis time: 45 min / Sample

After the addition, both sides of the DNPH cartridge were sealed and kept in that state for a certain time, and then the same extraction operation was performed. After the addition, the amount collected was compared with a recovery rate of 1 when it was extracted quickly without taking any time.
DNPH formaldehyde drops to about 80% after 1 hour, and remains at the same level, but DNPH acrolein drops to about 30% after 1 hour, and then continues to fall slowly. It was.

  From this result, it can be seen that, compared to DNPH-formaldehyde, DNPH-acrolein undergoes further dimer and trimer state changes after the derivatization reaction, making measurement impossible in a short time. It should be noted that there was no difference in the tendency of the recovery rate when the concentration was high or low.

FIG. 4 is a graph showing the relationship between the cartridge temperature and the recovery rate by adding a high concentration of acrolein (0.13 μg / mL) under the same experimental conditions as in Example 1. It is known that the first-stage derivatization reaction between a carbonyl compound and DNPH proceeds rapidly even at low temperatures. Therefore, whether the temperature dependence of the dimerization and trimerization reaction was observed was confirmed by cooling the entire cartridge in the low temperature tank of the collection device of FIG. Each temperature indicates a low-temperature tank set temperature.
(1): -20 ° C
(2): -15 ° C
(3): 2 ° C
(4): 7 ° C

  In the case of 7 ° C., it can be seen that the recovery rate is already about 60% after 30 minutes and drops to about 30% after 2 hours. The drop in the recovery rate became smaller as the temperature decreased, and a high recovery rate of about 90% was confirmed even after 2 hours at −20 ° C. That is, at −20 ° C., the remaining rate of DNPH-acrolein is high, and it is considered that the dimer / trimerization reaction did not proceed and the change with time could be prevented.

  Based on the results of Example 2, an automobile exhaust gas, which is an actual sample, was used as a sample, and an experiment was conducted to confirm the cooling effect of the collection part. FIG. 5 shows a schematic diagram of the experimental collection device. The exhaust port 1 of the automobile exhaust gas is heated to 60 ° C. to prevent moisture condensation, and is then branched in three directions by the connector 3. Connected to one side is a buffer cartridge 4 and a collection cartridge 5 cooled in a low temperature bath of −20 ° C., one is a room temperature DNPH cartridge 5 used in the conventional method, and the other is connected to an impinger 12 containing an absorbing solution. At the same time, exhaust gas was sucked with a pump under the same conditions and collected. The measurement method using the absorbing solution is difficult to handle and has poor detection sensitivity, but the effect of variations in the blank value is small, and it is known that there is almost no decrease in the concentration of the target acrolein. I decided to think.

<Experimental conditions> Collection:
Cartridge: inner diameter 8.8mm length 39.7mm
Collection agent: DNPH impregnated silica gel particle size 120 μm Packing amount 300 mg
Absorbent: DNPH hydrochloric acid solution 2g / L 40mL
Sample: Automobile exhaust gas (idling 40 sec, 1 min, 2 min)
Collection flow rate: 1 L / min
Collection time: 30 min
(1): Absorption liquid method (2): Cooling collection method according to the present invention (3): Conventional room temperature collection method

After extraction, HPLC:
Mobile phase: A: Water / acetonitrile = 50/50
B: Acetonitrile 100
Gradient: B: 0 to 60% (30 min) 60% (35 min)
Mobile phase flow rate: 1 mL / min
Column: Zorbax ODS 4.6 mmI. D. × (15 + 25cm)
Column temperature: 50 ° C
Detector: UV / VIS (wavelength 365 nm)
Injection volume: 10 μL
Analysis time: 45 min / Sample

FIG. 6 shows the result of collecting and extracting the exhaust gas after idling the automobile engine for 40 seconds, 1 minute, and 2 minutes. (In all cases, the atmosphere was collected and the total collection time was 30 minutes.)
In all cases, the concentration in the absorption liquid method considered to be the reference value and the concentration of the cooled collection cartridge 5 showed almost the same result. In the case of room temperature, the concentration is approximately 50%, and it is considered that the dimer and trimerization reactions probably proceeded and are no longer measured. Therefore, it was confirmed that cooling of the collection cartridge is very effective for stable, accurate and highly sensitive measurement.

FIG. 7 shows the result of actually measuring the set temperature and the cooling state of each part by attaching a thermocouple to each part of the collection device.
<Experimental conditions> Collection:
Cartridge: inner diameter 8.8mm length 39.7mm
Collection agent: DNPH impregnated silica gel particle size 120 μm Packing amount 300 mg
Sample: Atmospheric gas Collection flow rate: 1 L / min
Collection time: 20 min
Setting block temperature: -20 ° C
Measurement parts (1): Heated part at 60 ° C. by heat hose 2 (2): Connector 3 internal gas (3): Buffer cartridge 4 inlet partial carrier surface (4): DNPH cartridge 5 inlet partial carrier surface (5): Aluminum Block 8

  The temperature of the buffer cartridge 4 connected to the upstream side as the first stage was stabilized at 5 ° C. in about 8 minutes from the start of cooling, and then the installed collecting cartridge 5 was stabilized at about −10 ° C. Even though the gas inside the connector is kept at 40 ° C., it is considered that the buffer cartridge 4 connected to the front and upstream side performs a sufficient buffering action to achieve efficient heat exchange.

  Further, when the collection flow rate is increased to 1.8 L / min, a lot of warmed gas flows, so the temperature of both cartridges rises, the buffer cartridge 4 is about 17 ° C. in about 20 minutes, and the collection cartridge 5 is After about 30 minutes, the temperature became stable at 0 ° C.

  FIG. 8 shows the actual temperature measurement results of each part when the collection flow rate is 0.5 L / min, the collection time is 30 minutes, and the set temperature of the aluminum block 8 is −10 ° C. Other conditions are the same as in the case of the collection flow rate of 1 L / min shown in Example 4, and the plots of the graphs also correspond in the same manner.

  The temperature of the buffer cartridge 4 was stabilized at about 14 ° C. in about 20 minutes, and the collection cartridge 5 was stabilized at about 2 ° C. Although the buffer cartridge 4 exceeds 10 ° C., if the flow rate is reduced to 0.5 L / min, the collection cartridge 5 is stably cooled to about 2 ° C. even if the set block temperature is increased to −10 ° C. It was confirmed that

  FIG. 9 shows the results of measuring harmful air pollutants in the exhaust gas for each component in order to examine the collection cooling temperature. Since the concentration in the exhaust gas, which is the actual sample, is not constant, the conventional collection of 60 ° C. heating without cooling is performed at the same time, and it is set to 1, and the ratio with the case of cooling by the method of the present invention is graphed. The change in concentration was confirmed.

  The cooling temperature of the aluminum block 8 in the low-temperature tank 9 is set to 7 temperatures from 25 ° C. to −40 ° C. which are room temperature, and the temperature at a plurality of locations of the collecting cartridge 5 is measured simultaneously. confirmed.

<Experimental conditions> Collection:
Cartridge: inner diameter 8.8mm length 39.7mm
Collection agent: DNPH impregnated silica gel particle size 120 μm Packing amount 300 mg
Sample: Diesel exhaust gas Collection flow rate: 0.5 L / min
Collection time: 30 min
Setting block temperature: 25 ° C, 10 ° C, 0 ° C, -10 ° C, -20 ° C, -30 ° C, -40 ° C
Measurement components (1): acrolein (2): formaldehyde (3): acetaldehyde (4): methacrolein (5): benzaldehyde (6): m-tolualdehyde

After extraction, the HPLC conditions are the same as in Example 3.
In the graph, there are portions where the plots are difficult to overlap, so the original numerical ratios are also shown in Table 1.

  It was found that the concentration of acrolein indicated by ○ is almost stable when the cooling temperature of the aluminum block 8 is 0 ° C. or less, and is about 2.7 times the concentration during normal collection. The concentration at that time was a minimum value of 0.11 μg / mL and a maximum value of 0.40 μg / mL. When the cooling temperature of the aluminum block 8 was 0 ° C., the average temperature of the collection cartridge 5 was 8 ° C., and the maximum temperature was 9 ° C. In the entire set temperature range, the maximum error between the average temperature and the maximum temperature was 3 ° C., and the average error was about 1.4 ° C. From the above, it can be considered that a reliable measurement can be performed if the carrier temperature (average value) is cooled to 10 ° C. or less in consideration of 2 ° C. average error at 8 ° C. from the above.

  On the other hand, with respect to the lower carbonyl compounds other than acrolein, no change in collected amount due to temperature change was observed. The respective component concentrations are shown in Table 2 below.

  That is, it is considered that the temperature change acts to suppress the dimer and trimerization reaction without affecting the DNPH derivatization reaction itself. Therefore, it is considered that the present invention can be applied as it is without any problem to the simultaneous quantitative analysis of the lower carbonyl compounds which are harmful air pollutants such as aldehydes and ketones, which is an advantage of the conventional cartridge collecting method.

  From Example 4, it was confirmed that the carrier surface of the collection cartridge 5 was kept at 0 ° C. when the set temperature of the low temperature tank was −20 ° C. Therefore, it is confirmed that the apparatus of the present invention that uses the buffer cartridge 4 on the upstream side and cools the collection cartridge 5 with the aluminum block 8 in the low temperature tank 9 set at −20 ° C. satisfies the reliable collection condition. It was done.

  In addition, when the flow rate is small, it has been confirmed that the carrier surface temperature of the collection cartridge 5 is 10 ° C. or less even when the set temperature of the low temperature bath is −10 ° C. Therefore, it has been confirmed that by using the cooling set temperature according to the flow rate, the reasonable and reliable collection conditions are sufficiently satisfied.

Conventional collection device schematic explanatory diagram Schematic explanatory diagram of the collection device according to the present invention Figure showing the recovery rate of DNPH-acrolein and DNPH-formaldehyde at room temperature The figure which shows the recovery rate of DNPH-acrolein by the temperature change of this invention Schematic diagram of the embodiment of the present invention The figure which shows the automobile exhaust-gas collection analysis result by this invention and a prior art example Temperature change measurement diagram of the collecting device according to the present invention Temperature change measurement diagram of the collecting device according to the present invention The figure which shows collection temperature dependence results, such as acrolein by this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outlet 2 Heat hose 3 Connector 4 Buffer cartridge 5 Collection cartridge 8 Aluminum block 9 Low temperature tank 10 Temperature control apparatus 11 Sample conduit 111 Sample conduit 12 Impinger

Claims (12)

  In the measurement of a trace amount of harmful air pollutants, the sample impregnated with DNPH is cooled to cool the carrier impregnated with DNPH, and the DNPH reacts with the lower carbonyl compound in the sample. And a method for collecting a lower carbonyl compound.   The method for collecting a lower carbonyl compound according to claim 1, wherein the cooling temperature is 10 ° C or lower.   The method for collecting a lower carbonyl compound according to claim 1 or 2, wherein the cooling uses a collection cartridge in which a carrier impregnated with DNPH is installed.   The method for collecting a lower carbonyl compound according to any one of claims 1 to 3, wherein the collection uses a collection cartridge filled with carrier particles impregnated with DNPH.   The method for collecting a lower carbonyl compound according to any one of claims 1 to 3, wherein the collection uses a collection cartridge provided with an integrated porous body impregnated with DNPH.   The method for collecting a lower carbonyl compound according to any one of claims 1 to 5, wherein a buffer function for heat exchange of the sample is performed before the collection.   The method for collecting a lower carbonyl compound according to claim 6, wherein a buffer cartridge provided with a carrier is used for the buffer action.   The method for collecting a lower carbonyl compound according to claim 6 or 7, wherein the carrier for the buffer action is silica gel.   9. In collecting the sample, the sample is sent to the collecting cartridge in which the carrier impregnated with DNPH is installed next to the first stage and the buffer cartridge. A method for collecting the lower carbonyl compound as described.   The method for collecting a lower carbonyl compound according to any one of claims 1 to 9, wherein the lower carbonyl compound is acrolein.   Collection of a lower carbonyl compound characterized in that a sample cartridge introduced into a low-temperature bath is detachably provided with a collection cartridge having a carrier impregnated with DNPH, and the temperature of the collection cartridge is freely controlled. apparatus.   12. The apparatus for collecting a lower carbonyl compound according to claim 11, wherein a buffer cartridge is detachably provided on the upstream side of the collection cartridge of the sample conduit introduced into the low-temperature tank.

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